When administering physiological fluids to a patient, it is desirable to remove excess air or other gasses prior to introduction of the fluids into the patient.
Devices are known which eliminate gasses from fluids to be applied to a patient. For example, U.S. Pat. No. 4,190,426 (Ruschke) teaches a gas separating and venting filter wherein gas is removed from a fluid by a liquid-wetting (hydrophilic) membrane which divides the device into inlet and outlet chambers. The inlet chamber includes a liquid-repellent (hydrophobic) membrane which passes gas removed by the liquid-wetting filter to the atmosphere.
U.S. Pat. No. 4,413,990 (Mittleman) and U.S. Pat. No. 4,571,244 (Knighton) teach devices which also rely upon liquid-wetting filters to remove gasses. In the Mittleman device, a membrane valve is placed at the bottom of a burette for removing gasses. The Knighton apparatus includes a horizontally disposed cylinder having a liquid-wetting filter at one end and a liquid-repellent filter at an opposite end. The fluid to be treated is introduced at a mid-point of the cylinder.
U.S. Pat. No. 4,572,724 (Rosenberg et al.) teaches a blood filter for use in a cardiopulmonary by-pass system. An upper chamber is arranged to receive blood and cause it to flow in a circular direction whereby air is separated by the centrifugal forces on the blood. Air bubbles above a predetermined size which were not removed in the first chamber are removed by a cylindrical filter made of a pleated screen.